The present invention relates generally to the field of orthodontics, and more particularly to an apparatus for bonding an orthodontic bracket to a tooth and a method for making the same.
The fundamental objectives in orthodontics are to move a patient's teeth to a position where the mechanical function of the dentition is optimized and to improve the aesthetic appearance of the patient's teeth. The traditional method that orthodontists use is to attach brackets and wires onto the patient's dentition. Once mounted on the teeth, the wires exert continual light forces through the brackets onto the teeth. These forces initiate the body's biological bone remodeling response and the teeth gradually progress toward their desired final positions. During the treatment period, the treatment professional reactively adjusts the wires and bands to provide a new force and move the teeth toward their desired or final destination.
Orthodontic brackets are often bonded directly to the patient's teeth using a small quantity of adhesive placed on the base of each bracket and the bracket is then placed on a selected tooth while the patient is in the dental chair. Once the adhesive has hardened, the bracket is bonded to the tooth with sufficient strength to withstand subsequent orthodontic forces as treatment progresses. One shortcoming with this technique is the difficulty in accessing the optimal position on the tooth surface for bracket placement on severely crowded teeth or in teeth where the bonding surface is obstructed by teeth in the opposing arch during jaw closure. With posterior teeth, the treatment professional may have difficulty seeing the precise position of the bracket relative to the tooth surface due to limited working space. Also, for most bonding agents, it is necessary to minimize moisture contamination from the patient's saliva for adequate bonding strength. This can prolong the procedure and also unduly impair the accuracy of placement of the brackets on the teeth.
One way to overcome some of the limitations of direct bracket placement is with indirect bonding. Typically, a routine impression of each of the patient's upper and lower dental arches is taken and either sent to a lab or used in the office to create a replica plaster model of each impression after the patient has left the office. Brackets are bonded to the sealed plaster models using a temporary adhesive. A transfer tray is then made by placing matrix material, usually consisting of silicone rubber, over both the model and brackets. The matrix material then assumes a configuration that matches the shape of the replica teeth of the plaster model with the brackets in the desired position. The matrix material then polymerizes and hardens to form a tray. The temporary adhesive is removed, and permanent adhesive is placed on the base of each bracket in the tray, which is then placed over matching portions of the patient's dental arches. Since the configuration of the interior surface of the tray closely matches the respective portions of the patient's dental arches, each bracket location is transferred onto the patient's teeth at precisely the same location that corresponds to the previous location of the same bracket on the plaster model. The adhesive is hardened and the matrix removed, leaving the brackets in the desired positions. This indirect method, however, is labor intensive and fabrication of the intricate details (corresponding to the details of the patient's teeth) of the tray is complex and time-consuming.